what does air pressure do to the freezing, melting ad boiling point
answered below.
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Air pressure affects the freezing, melting, and boiling points of substances. To understand how it works, we need to discuss the concepts of pressure and phase changes.
Pressure is a measure of the force exerted by a substance per unit area. When it comes to gases, pressure is caused by the constant collision of gas particles with each other and with the walls of the container they are in.
Now, let's talk about phase changes. The phase of a substance refers to its state - solid, liquid, or gas. When a substance changes from one phase to another, it goes through a phase change. For example, when water freezes, it changes from a liquid to a solid, and when it boils, it changes from a liquid to a gas.
Generally, increasing the pressure on a substance increases its melting and boiling points, while decreasing the pressure lowers them. This relationship is known as the phase diagram.
When pressure is increased, the particles are compressed, making it more difficult for them to move freely. As a result, the substance requires a higher temperature to overcome the increased pressure and change phase. Conversely, decreasing the pressure allows the particles to move more freely, making it easier for a substance to change phase at a lower temperature.
For example, at standard atmospheric pressure (1 atm), water boils at 100 degrees Celsius, but at high altitudes where the air pressure is lower, the boiling point decreases. This is why boiling water takes longer at higher altitudes.
Similarly, if pressure is increased on ice, the melting point will also increase. That's why pressure is often used to lower the freezing point of some substances, allowing them to stay liquid at lower temperatures. This phenomenon is applied in antifreeze solutions in cars.
In summary, air pressure affects the freezing, melting, and boiling points of substances by influencing the ease with which particles can change their phase. When pressure is increased, the phase changes require higher temperatures to occur, while decreasing the pressure lowers the required temperatures.